WASHINGTON, Oct. 9 (UPI) -- The number of Americans who don't identify with a religion has grown, with a fifth of adults saying they're religiously unaffiliated, a Pew survey indicated.

The religiously unaffiliated includes more than 13 million self-described atheists and agnostics as well as nearly 33 million people who say they have no particular religious affiliation, the Pew Forum on Religion and Public Life survey released Tuesday indicated.